Mining machine having rectangular thrust transmitting conveyor column

ABSTRACT

A mining machine comprises a laterally elongated cutting head including  ms for cutting an earth formation, a laterally elongated thrust transmitting column connected to and extending rearwardly from the cutting head, and a power head connected to the rear of the column and operative to thrust the cutting head forward into the earth formation by means of the interposed column. The column carries a non-thrust transmitting column conveyor for carrying fragments cut from the formation from the cutting head to the power head.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to the extraction of minerals from theearth and is especially adapted for the mining of coal. The need forsources of energy has multiplied rapidly over the past several decadesas technology has developed and society has become increasinglymechanized. At the present time almost all of our energy needs are beingmet by combustion of various forms of fossil fuels such as coal, naturalgas, and petroleum. Our increased energy needs dictate that the meansfor extracting these fuels from the earth be improved and made asefficient as possible. At the same time, it is imperative thatdeleterious effects on the environment due to such extraction beminimized.

Coal normally is found deposited in seams or layers interspersed withlayers or strata of rock, soil, or other earth formation. The bestmethod of mining would involve removing as much coal as possible fromthese layers with minimal removal of the surrounding non-coal strata andminimal disturbance or defacing of the terrain in the area. It is alsonecessary, where coal has been removed from a seam without disturbingthe surface terrain, to leave adequate supporting structure in the seamto prevent cave-ins. Often a preliminary excavation is made, either fromthe surface or underground, to expose a wall containing one or moreseals of coal. The coal is then removed by working from the wall intothe seam.

Hand mining techniques in which the miners must enter the area of theseam as it is being mined are obviously dangerous and slow.Additionally, these techniques result in a great deal of waste if thecoal seam is thin since enough material must be removed to allow theminers to enter even if much of the material is non-coal earthformation.

For these reasons, attention has been directed to the development ofremote control apparatus for removing coal from a seam without the needfor workers entering the seam. In particular there is need for suchapparatus which is adaptable for the mining of thin seams.

2. Description of the Prior Art

One approach to solving this problem involved drilling into the seamfrom the exposed wall with an auger type drill. In some cases theleading end of the auger was provided with cutting means so that theauger itself served only as a conveyor for the cuttings and atransmitting member for the drilling thrust and torque, see e.g. U.S.Pat. No. 2,948,520. By using an auger of sufficiently small diameter, itwas possible to remove coal from a thin seam without cutting into thesurrounding rock. However, the only way of adapting the machine formining a seam of another thickness was to replace the auger by anotherone of different diameter or to provide radially extensible auxiliarycutters. Furthermore, the diameter of the auger and/or cutters limitedthe width as well as the height of the hole which could be bored. Thiswas less than satisfactory because the coal seams are usuallysubstantially continuous in lateral extent.

Several attempts have been made to devise a machine which could removemore coal from the seam in a single pass by drilling a hole which waswider than the height of the seam. Two such machines are shown in U.S.Pat. No. 3,746,110 and British Pat. No. 800,864. Each of these machineshas a cutting head which is wider than it is high. Thrust is transmittedto the cutting head by two parallel strings of rods in the machine ofthe British Patent and by two or more strings of auger segments, muchthe same as rods, in the machine of the U.S. Patent. Both of thesemachines suffer from the same basic disadvantages. In an effort tobetter distribute the drilling thrust across the cutting head, two ormore strings of rods or the like are used. However, this introduces newproblems of keeping these strings aligned and the forces balanced. Eventhough the two strings may be tied together laterally at a relativelyfew spaced locations along their lengths, they still act essentially astwo separate strings and this alignment and balance is difficult, if notimpossible, to achieve.

Another difficulty is that the strings of rods or auger segments areflexible under the high forces necessary for drilling. They tend tobuckle, whip, etc. This makes the machine generally unstable,susceptible to failure of various parts, and difficult to control andsteer from a remote location outside the hole being drilled. Thistendency toward whipping and the like is evidenced by the fact that therod strings of the machine of the British Patent are provided withupstanding guides which brace the strings against the roof of the holeto combat the whipping action.

Still another problem with these two machines is that the conveyors areunprotected against any material which might fall from the roof of thehole being drilled. This can jam the conveyor and in some cases can evenresult in the entire machine being caught in the hole. In this situationthe expensive cutting head is either lost entirely, or it must beforcefully pulled from the hole resulting in severe damage to variousparts of the machinery, particularly the conveyor. In the machine of theU.S. Patent, the conveyors are subjected to even worse abuse by virtueof the fact that they are the sole means of transmitting the drillingthrust and torque to the cutting head.

SUMMARY OF THE INVENTION

The drilling machine of the present invention includes a laterallyelongated cutting head including means for cutting into the coal andbreaking it away in fragments. A thrust-transmitting column, alsolaterally elongated, is connected to the rear of the cutting head. Apower head designed to be stationed outside the hole adjacent the wallis connected to the rear of the column and thrusts the cutting headforward into the formation by means of the column. The column hassufficient cross-sectional dimension and internal structural strength totransmit thrust as a column, albeit that it is disposed generallyhorizontally rather than vertically, without flexing, whipping, etc.Thus, it can be used not only to transmit thrust, but also to guide andcontrol the cutting head in gross steering.

The column is preferably comprised of a plurality of column modulesremovably connected end-to-end. The forwardmost module is removablyconnected to the cutting head, and rearwardmost module is removablyconnected to the power head. As drilling progresses, the power head isperiodically disconnected from the rear module then in place and pulledback so that a new rear module can be interposed therebetween toincrease the length of the column.

A non-torque-transmitting column conveyor is carried by the column andextends along substantially its entire length. The column conveyor ispreferably comprised of a plurality of conveyor segments disposed inend-to-end relation, each of the conveyor segments being carried by arespective one of said column modules. Each of the modules has a mainbody which preferably defines a box-like structure having a top cover.The respective conveyor segment is disposed within the box-likestructure beneath the top cover for protection.

The forwardmost column module may be modified to serve as a controlmodule for fine steering and control of the cutting head. It preferablycomprises both vertical and horizontal steering means which can beoperated by remote controls located outside the hole. The horizontalsteering means preferably comprises a single side steering shoeselectively laterally extensible and retractable from one side of thecontrol module. The cutting head includes means operative to cause thecutting head to bear laterally toward the side on which the sidesteering shoe is located. Then the front of the drilling machine can besteered in a horizontal direction by pushing against the side wall ofthe hole being bored with the side steering shoe to resist to varyingdegrees the tendency of the cutting head to bear to that side.

The machine may include means for pivoting the cutting head with respectto the control module. This provides vertical sweep to accommodatevarious thicknesses of coal seams. The control module is preferablyprovided with means for detecting the thickness of the layer of coalremaining at the top of the hole to advise the machine operator of thevertical steering and sweep needs.

As successive holes are drilled side-by-side, pillars of formation areleft between the holes to support the formation above. Each new hole islocated on that side of the last preceding hole which corresponds to theside of the control module on which the side steering shoe is located.Then as the new hole progresses, there should be a supporting pillar offormation on the side of the machine opposite the side steering shoe andsolid unmined formation adjacent the side steering shoe. The controlmodule may include sensor means for detecting the presence of theadjacent supporting pillar to advise the operator of the horizontalsteering needs. The sensor means can also be operative to detect somefactor, e.g. thickness, which is indicative of the strength of thepillar.

The power head of the machine may include a track frame and a driveassembly mounted thereon. Primary reversible drive means are providedfor moving the drive assembly longitudinally along the track frame andthereby thrusting the connected column and cutting head forward orpulling them back. Auxiliary drive means may be included to provideadditional force, for example, to pull the cutting head from the hole ifit should become jammed or stuck.

It is thus a principle object of the present invention to provide adrilling machine comprising a laterally elongated column fortransmitting thrust from a power head outside a hole being drilled to acutting head within the hole.

Another object of the invention is to provide a mining machine having alaterally elongated thrust-transmitting column comprising a plurality ofmodules connected end-to-end.

A further object of the invention is to provide a mining machine havinga modular thrust transmitting column which carries and protects asectioned non-thrust-transmitting column conveyor.

Yet another object of the invention is to provide a mining machinehaving a modular thrust-transmitting column, a forwardmost module ofwhich is modified to serve as a control module.

Still a further object of the invention is to provide a mining machinein which horizontal steering is accomplished by a single laterallyextensible and retractable shoe and in which the cutting head inoperation tends to bear toward the side of the machine on which saidshoe is located.

One more object of the invention is to provide a mining machine with apower head having primary reversible drive means and auxiliary drivemeans.

Other objects, features, and advantages of the invention will be madeapparent by the following description of a preferred embodiment, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic perspective view of the mining apparatus of theinvention in operation with parts broken away.

FIG. 2 is a top plan view of the cutting head and an adjacent portion ofthe control module with parts broken away.

FIG. 3 is a side elevation of the cutting head and an adjacent portionof the control module with parts broken away and parts shown in section.

FIG. 4 is a top plan view of a portion of the control module showing thecontrol and steering shoes.

FIG. 5 is a side elevation on line 5--5 of FIG. 4 with parts broken awayand parts shown in section.

FIG. 6 is a sectional view along lines 6--6 in FIG. 4 showing one of thetop control shoes and the top sensing means in retracted position.

FIG. 7 is a view similar to that of FIG. 6 showing the control shoe inextended position.

FIG. 8 is a top plan view of one of the column modules with parts brokenaway and parts shown in section.

FIG. 9 is a side elevation of the module of FIG. 8.

FIG. 10 is an end elevation on lines 10--10 in FIG. 9.

FIG. 11 is an end elevation on lines 11--11 in FIG. 9.

FIG. 12 is a sectional view along lines 12--12 in FIG. 8 showing thefemale lock assembly of the column module and also showing the male lockassembly of an adjacent module prior to connection.

FIG. 13 is a view of the apparatus of FIG. 12 in connected position.

FIG. 14 is a sectional view along lines 14--14 in FIG. 12.

FIG. 15 is a side elevation of the power head.

FIG. 16 is a top fragmentary plan view of a portion of the power head onlines 16--16 in FIG. 15 and with parts broken away and parts shown insection.

FIG. 17 is an enlarged side elevation of the power head with partsbroken away.

FIG. 18 is a front elevation of the power head on lines 18--18 of FIG.17.

FIG. 19 is a section view on lines 19--19 in FIG. 17 showing theauxiliary drive means.

FIG. 20 is a fragmentary sectional view on lines 20--20 of FIG. 9.

FIG. 21 is a fragmentary view of a portion of the apparatus of FIG. 7showing a second embodiment of the sensor.

FIG. 22 is a fragmentary view of the locking member of the femaleconnection assembly of FIGS. 12-14.

FIG. 23 is a partial sectional view on lines 23--23 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 there is shown a pit 10 which may have been formedby partial strip mining of the area being mined. Alternatively, the pit10 may be formed specifically to provide a site for the mining apparatusof the invention. In any event, the excavation of the pit 10 exposes awall 12. The wall 12 shows the stratification of the formation behindit, particularly revealing a lower thin seam of coal 14 and an upperlayer of rock and/or soil 16. The mining machine includes a power head18 located in the pit 10 facing the wall 12. The power head 18 includesa base frame 22 anchored to the floor of the pit 10, a track frame 20vertically pivotally mounted on the base frame 22, and a drive assembly24 mounted on the track frame 20 for longitudinal movement toward andaway from the wall 12. Specific structural and operational details ofthe power head 18 as well as other parts of the mining machine will bedescribed below, it being the intention at this point to generallydescribe the mining apparatus as a whole and its operation.

The machine is shown in the process of drilling a hole 26. Extendinginto this hole 26 from the power head 18 is a thrust-transmitting columncomprising a plurality of column modules 28 and 28' connectedend-to-end. The forwardmost column module 28' is connected to a cuttinghead 30. The cutting head 30 includes cutting means which break away theformation to form the hole as the cutting head is thrust forward by thepower head 18 via the column modules 28', 28. Specifically, the driveassembly 24 is connected to the rear end of the rearwardmost one of thecolumn modules 28 shown on the track frame 20. As the drive assembly 24moves forward on the track frame 20, the entire column with the cuttinghead is thrust forward until the rearwardmost column, connected directlyto the drive assembly, is almost entirely within the hole 26. At thispoint, the drive assembly is detached from the rearwardmost columnmodule and moved back to the rear of the track frame 20. A crane 34 thenlifts another module 28 from a stack 32 in the pit by means of vacuumpads 36 and places it on the track frame between the column and thedrive assembly. The drive assembly and the remainder of the column arethen connected to this new module, now the rearwardmost one, anddrilling begins again.

It should be noted here that the cutting head end of the machine will beconsidered the "front" end of the machine, while the power head end willbe the "rear." Accordingly, a forward direction will be generally fromthe pit into the wall and a rearward direction will be from the walltoward the pit. Many coal seams are not truly horizontal. Thus, themachine will often operate at an angle. However, for convenience, theterms "horizontal" and "vertical" as used herein will be defined withrespect to the machine itself as it would be disposed if operating trulyhorizontally.

A pair of parallel screw type conveyors 38 extend longitudinally throughthe column and seve to convey fragments cut from the formation by thecutting head 30 out of the hole 26. The conveyors are carried by thecolumn in such a way that they are not subjected to and do not transmitany substantial part of the drilling thrust. When the fragments orcuttings reach the rear of the column, they are conveyed upwardy andrearwardly by screw type power head conveyors 40 in the drive assembly.From conveyors 40 the cuttings are dropped onto a belt conveyor 42extending transversely across the back of the drive assembly. Conveyor42 in turn drops the cuttings onto another endless belt conveyor 44which carries them rearwardly to still another conveyor 46 by which theyare loaded into trucks or suitable containers. It will be noted that thebelt conveyor 44 extends along one side of the power head 18 so that itcan catch the cuttings from conveyor 42 regardless of the position ofthe drive assembly 24 on the track frame 20.

Several generally parallel holes have been drilled in the coal 14. Afterthe completion of each hole, the cutting head 30 is withdrawn from thehole by reversing the procedure used in drilling. In particular, thedrive assembly 24 is moved rearwardly on the track frame 20 until therearwardmost module can be removed. The drive assembly 24 is then movedforward, attached to the next module, and moved back again. The cuttinghead 30 is finally removed from the hole, by connecting it directly tothe drive assembly 24. The machine is then moved a short distance to theright and a new hole is begun by thrusting the cutting head 30, which isstill directly connected to the drive assembly, into the formation.Column modules can then be added one by one as the hole progresses.

A supporting pillar of formation is left between the old hole and thenew hole. For example, after completion of hole 52, hole 48 was drilledleaving supporting pillar 50. Similarly, there is a supporting pillar 54between hole 48 and the hole 26 shown in the process of being formed. Inthe embodiment shown, the machine always moves from left to right. Thuswhile each hole is being formed, there is a supporting pillar to itsleft and solid unmined formation to its right. The cutting head 30 isprovided with means to cause the cutting head, while drilling, to bearto the right.

The forwardmost column module 28' is modified to serve as a controlmodule. It includes a side steering shoe laterally extensible andretractable from its right side. Thus, the front of the machine can besteered in the horizontal direction by pushing against the righthandwall of hole 26 to resist to varying degrees the tendency of the cuttinghead to bear to the right. It will be appreciated that the machine couldbe designed to move from right to left, in which case the cutting headwould be designed to bear to the left, and the side steering shoe wouldbe located on the left of control module 28'.

In addition to the side steering shoe, the control module 28' includesbottom shoes for vertical steering, top control shoes for reaction toforces generated by the cutting head, and means for vertically pivotingor sweeping the cutting head with respect to the control module. Thecontrol module also contains sensing means which make the steering andsweeping needs known to the operator. These sensing and control devicesare all connected, e.g. electronically or hydraulically, to a controlstation outside the hole. The control station might be located in thecrane 34. The control station contains readout apparatus for the sensingmeans, switches or the like for operating the control and steering shoesand the sweep means, and means for operating the various motors,hydraulic rams, etc. on different parts of the machine.

Turning now to a more detailed description of the apparatus, FIGS. 2 and3 show the cutting head 30 and the front portion of the control module28'. The mid portion of control module 28' is shown in FIGS. 4 and 5.Cutting head 30 comprises a pair of spaced apart side bars 56. The bars56 are joined at their front ends by a transverse shaft 58 mounted forrotation in the bars 56 by suitable bearings. The rear ends of bars 56are pivotally connected to the front of the control module 28' byhorizontal pins, one of which is shown at 60. Bars 56 are also connectedby a transverse bracing rod 62 intermediate their front and rear ends.Mounted near the rear end of each bar 56 is a motor 64. Each motor 64 isoperably connected to a sprocket wheel, one of which is shown at 66,rotatably mounted in the rear end of the respective bar 62. Eachsprocket wheel 66 drives an endless chain 68 which extends around theperiphery of the respective bar 62 in a vertical plane. Each of thechains 68 engages a respective sprocket (not shown) connected to theshaft 58 to rotate the latter.

A plurality of cutting picks 70 are rigidly mounted on each chain 62 anddisposed at an angle to cut into the formation as the chain moves in thedirection of the arrow A in FIG. 3. Thus the two chains together withtheir picks 70 form a first pair of cutting means. At each end of theshaft 58 is a cutting wheel 72, and each of these wheels 72 carries aplurality of picks 74 disposed at angles to cut into the formation whenthe shaft 58 rotates. Thus each wheel 72 with its picks 74 forms anadditional outboard cutting means. A fifty cutting means, known as thecenter cutter, is formed by a plurality of picks 76 rigidly mounted onthe shaft 58 and disposed at angles to cut into the formation as theshaft rotates. The picks 76 are arranged in a helical pattern, and thehelix which they form is wound in a direction which cooperates with thedirection of rotation of the shaft 58 to cause the cutting head inoperation to bear toward a desired side. As mentioned above, the machinein the embodiment shown is designed so that the cutting head will beartoward its own right side (left side as viewed in FIG. 2). Accordingly,the picks 76 are arranged in the form of a right hand helix when viewedlooking from the back toward the front of the machine (left hand helixas viewed in FIG. 2) for clockwise rotation of shaft 58 as viewed fromthe right side as in FIG. 3.

Also wound on the shaft 58 are a pair of helical conveyors 78 and 80.These are wound in opposite directions to direct the fragments cut bypicks 76 toward the center of shaft 58. A scoop 82 (FIGS. 2 and 23)extends from the control module 28' forward along the floor of the holebeing drilled and under the rear portion of the cutting head 30. Thebottom of scoop 82 is pivoted to control module 28' by pins 83. The topof scoop 82 is connected to control module 28' by pins 85 riding inslots 87 so that scoop 82 has some vertical flexibility. The controlmodule 30 carries a pair of parallel helical conveyor sections 84' whosefront ends extend forward from the control module 28' over the scoop 82and between the rear portions of the bars 56 of the cutting head 30. Asthe machine moves forward in the hole, the fragments cut by the picks 76and conveyed toward the center of the shaft 58 by the conveyors 78 and80 are scooped up by the scoop 82 as it scrapes along the floor of thehole. These cuttings are then conveyed rearwardly through the controlmodule 28' by the conveyor segments 84'.

At each side of the front end of the control module 28' is a sidescraper 86. Scrapers 86 are disposed generally longitudinally of thecontrol module 28', but their rear ends are pivoted to the controlmodule by pins 88 so that their front ends can be moved laterally in andout to follow the side walls of the hole being drilled. A bottom scraper90 is rigidly connected to each of the side scrapers 86 near its frontend and extends laterally inwardly therefrom. Inboard of each scraper 86is a single acting hydraulic ram assembly 92 disposed generallylongitudinally of the control module 28'. Each of the ram assemblies 92has its cylinder pivoted to the main body of the control module and itspiston pivoted to the respective bottom scraper 90, both connectionsbeing for horizontal pivoting. Thus the front ends of the scrapers 86can be urged laterally outwardly against the formation by operation ofthe ram assemblies 92. Also mounted on the scrapers 90 are a pair oflaterally extending helical conveyors 94 which, together with scrapers90, extend into the scoop 82 through cut-outs 96 in its sides (see FIG.23). The scrapers 86 and 90 serve to gather the fragments cut by picks74 of the outboard wheels 72 and picks 70 of the chains 68 and directthem to the conveyors 94. Conveyors 94 in turn convey the cuttings intothe scoop 82 from which they are carried rearwardly by the conveyorsections 84'. Note that the scraper 86 and scoop 82 have been brokenaway in FIG. 3 for clarity.

As mentioned above, the rear ends of the bars 56 of the cutting head areconnected to the front of the main body of the control module 28 byhorizontal pins 60 for vertical pivotal movement with respect to thecontrol module. Each bar 56 has an upstanding ear 100 located generallyabove and slightly forward of the respective pin 60. On each side of themachine is a hydraulic sweep control ram assembly 98. Each of the ramassemblies 98 has its cylinder connected for vertical pivoting to themain body of the control module 28' and its piston connected to therespective ear 100 for vertical pivotal movement. Thus by retracting theram assemblies 98, the front of the cutting head 30 can be swept orraised vertically as shown in phantom at 30' in FIG. 3 to mine an areaof substantially greater vertical dimension that the cutting headitself. This allows the machine to extract maximum coal from seams ofvarious thicknesses or from one seam whose thickness varies from placeto place. Operatively connected to each ram assembly 98 are a servovalve 101 and a servo motor 103. The servo valve 101 and servo motor 103are used to set the stroke of assembly 98 at a desired length to providethe proper amount of sweep for the cutting head 30. Valve 101 and motor103 can also be used to cause the ram assembly 98 to automaticallyreciprocate in a cyclic manner.

It will be appreciated that the cutting head 30 is laterally elongated,i.e. its dimension from side to side is considerably greater than itsvertical dimension. One of the main uses of the machine is in miningthin seams, and the vertical dimension of the cutting head is primarilydetermined by the thinnest seam area the machine will be expected tomine. The lateral dimension of the cutting head is primarily determinedto allow a hole of maximum width to be drilled in a single pass whilestill leaving the pillars of formation between holes close enough toeach other to provide adequate support.

Referring now to FIGS. 4 and 7 there is shown the mid portion of thecontrol module 28'. For clarification in showing the various control andsteering assemblies, various structural details of the control module,particularly its main body, have been omitted from these figures. Atthis point suffice it to say that the structure of the main body of thecontrol module is similar to that of the other column modules 28, to bedescribed hereinafter. The main body generally comprises a rigidbox-like thrust-transmitting structure on which the other parts such asthe conveyor sections 84', scoop 82, scrapers 86, various ramassemblies, etc., are mounted.

As shown in FIGS. 4 and 5, the control module has a side steering deviceon its right side (lower side as seen in FIG. 4). As mentioned above,this arrangement is for a machine in which the cutting head will bear tothe right; the side steering device could be located on the left for amachine whose cutting head bears to the left. The side steering devicecomprises a side steering shoe 102. Shoe 102 is mounted on two pair oflinks 104 and 106 each having a laterally innermost stationary end and alaterally outermost swinging end. The stationary ends of the rear links104 are connected by vertical pins 108 to plates 110 which are rigidlyconnected to the main body of the control module. The swinging ends ofrear links 104 are pivotally connected to the rear end of shoe 102 andalso to the end of the piston rod of a hydraulic double acting sidesteering ram assembly 112 by a vertical pin 114. The front links 106have their stationary ends connected by vertical pins 116 to plates 118which are rigidly connected to the main body of the control module. Forconvenience, the cylinder of the side steering ram assembly 112 is alsoconnected to plates 118 by pin 116 although it could be pivoted to themain body of the control module by other means or in another location.The swinging ends of front links 106 are pivotally connected to thefront end of shoe 102 by vertical pin 120. The swinging ends of all fourlinks 104, 106 can swing rearwardly and laterally outwardly as shoe 102moves out to the position shown in phantom at 102'. Phantom lines 102'represent the maximum extent of shoe 102 and the solid lines representits fully retracted position in which the entire side steering devicelies within a recess 122 in the main body of the control module. It willbe appreciated that the shoe 102 could assume various positions betweenthese two extremes. Shoe 102 is laterally extended and retracted fromthe right side of the control module by means of the side steering ramassembly 112 which is disposed at an angle to move the shoe 102rearwardly and laterally outwardly when extended and forward andlaterally inwardly when retracted. Meanwhile, the links 104 and 106limit the travel of the shoe 102 and keep it parallel to the side of thecontrol module regardless of its position. The shoe 102 is brought tobear against the right side wall of the hole being drilled to resist thetendency of the cutting head to bear to the right during operation. Thefront of the machine can then be steered in the horizontal direction byresisting the tendency of the cutting head to bear right to varyingdegrees.

On the left side of the machine directly opposite the side steeringassembly is a sensing means illustrated diagrammatically at 124. Sensor124 senses the presence of a supporting pillar of formation to the leftof the hole being drilled (see 54 in FIG. 1). The sensor preferably alsosenses some factor indicative of the strength of the pillar, e.g. itsactual strength, its thickness, or its mass. The presence or absence ofthis pillar and its strength makes the horizontal steering needs knownto the operator of the machine who can then operate the side steeringdevice accordingly. Generally he may strive to maintain a more or lessuniform pillar thickness so that the hole will be generally parallel tothe last hole drilled. Alternatively, the readings from sensor 124 maybe electronically or otherwise transmitted directly to the controls forthe side steering device to cause automatic steering. The sensor 124 canbe any suitable type; for example, it might sense the adjacent pillar bytransmitting ultrasonic waves and timing the echoes, or it might makesimilar use of microwaves, beams of nucleonic particles, laser beams,low frequency waves, etc. Still another possibility involves the use ofa vibrator to strike the wall at a given frequency and means to measurethe transmission of the vibrations through the formation. The readingsfrom the sensor are transmitted to the machine operator at a controlstation outside the hole by any suitable means such as an electriccircuit (not shown). A sensor such as 124 allows for continuous remotemeasurement of the pillar while the machine is drilling. However it willbe appreciated that the pillar could be measured by a separate devicesuch as a core guage which would be inserted in the hole alongside themachine while the drilling was stopped for emplacement of a new columnmodule.

The control module also includes a pair of vertical steering devicesdisposed on opposite sides of the bottom of the control module. Thevertical steering devices are very similar to the side steering deviceexcept that their shoes are vertically extensible and retractable fromthe bottom of the control module. Each of the vertical steering devicescomprises a shoe 126 carried by a pair of rear links 128 and a pair offront links 130. The innermost ends of the links 128 and 130 arestationary and the outermost ends swinging. The stationary ends of therear links 128 of each vertical device are connected to plates 132 byhorizontal pins. Plates 132 are rigidly connected to the main body ofthe control module. The swinging ends of the rear links 128 of eachvertical steering device are pivotally connected to the rear end of theshoe 126 and also to the piston rod of a hydraulic double actingvertical steering ram assembly 134 by a horizontal pin. The stationaryand swinging ends of the front links 130 of each vertical steeringdevice are respectively connected to plates 136 and the front ends oftheir shoe 126 by horizontal pins. Plates 136 are rigidly connected tothe main body of the control module. Thus, as the shoes 126 are moveddownwardly and rearwardly by their respective vertical steering ramassemblies 134, the swinging ends of the links 128 and 130 also movedown and back in vertical planes to keep the shoes 126 parallel to thebottom of the control module. Because the links 128 and 130 are short,it is more practical to use a short ram assembly 134 having a shortstroke. Accordingly, the cylinder of the assemblies 134 cannot beconnected to plates 136 but are connected to respective ears 138 locatedbetween plates 132 and 136 on each vertical steering device and rigidlyconnected to the main body of the control module.

The solid lines in FIG. 5 show the fully retracted position of shoe 126in which the entire vertical steering device is disposed within a recess140 in the main body of the control module. The fully extended positionof shoe 126 is shown in phantom at 126'. Shoe 126 is moved between thesetwo positions by extending and retracting ram assembly 134. The operatorof the machine can steer the front of the machine vertically by varyingthe positions of the shoes 126 as they ride on the bottom of the holebeing drilled. He can also tilt the machine by extending one shoe 126more than the other. Either or both of the shoes 126 may comprise abottom sensor 135, similar to top sensors 137 to be described more fullybelow.

During operation, the cutting head 30 generates a high torque which maytend to lift the front of the machine off of the floor of the hole. Tocounteract this lifting, a pair of top control devices are provided onopposite sides of the top of the control module. Each of the top controldevices comprises a top control shoe 142 which can be urged upwardly bya top control ram assembly 144 to ride against the ceiling of the hole.Either or both of the top control shoes 142' may have a top sensor 137mounted thereon.

As best seen in FIGS. 6 and 7, the shoe 142 is carried by two pairs oflinks 146 and 148. Rear links 146 and front links 148 have theirstationary ends connected to respective plates 150 and 152 by horizontalpins. Plates 150 and 152 are rigidly connected to the main body of thecontrol module. Front links 148 have their swinging ends pivotallyconnected to the front end of the shoe 142 by a horizontal pin. Rearlinks 146 have their swinging ends pivotally connected to the rear endof shoe 142 by a horizontal pin. The piston rod of ram assembly 144 isconnected to shoe 142 slightly below the connections of links 146 by ahorizontal pin. The cylinder of assembly 144 is connected to an ear 154rigidly connected to the main body of the control module.

As with the steering shoes described above, the links 146 and 148 limitthe extent of shoe 142 and keep it parallel to the top of the controlmodule as it is extended and retracted from the top of the controlmodule by the ram assembly 144. FIG. 6 shows the shoe 142 in its fullyretracted position in which the entire top control device is disposedwithin a recess 156 in the top of the main body of the control module.FIG. 7 shows the shoe 142 in its fully extended position riding againstthe ceiling 158 of the hole. As with the vertical steering shoes, topcontrol shoes 142 can be independently operated to aid in or accommodatetilting of the machine.

Top and bottom sensors 137 and 135 are similar to the sensor 124.Sensors 137 may be operative to measure the thickness of a layer of coal170 remaining at the top of the hole adjacent another stratum 172 ofrock or the like. Sensors 137 might measure the thickness per se oflayer 170, or they might determine other factors which indicate whetherthe cutting head is moving too close to the stratum 172 or not closeenough. This allows a maximum amount of coal to be extracted from theseam without cutting into stratum 172 thereby causing waste and, if,stratum 172 is hard, damage to the cutting head. Bottom sensors 135 arepreferably identical to top sensors 137 but detect the thickness of thelayer of coal at the bottom of the hole (or other related factor).

Sensors 135, 137 may measure the thickness of the coal by producingultrasonic waves, low frequency waves, microwaves, beams of nucleonicparticles, laser beams, physical vibrations, etc. and measuring theirtransmission and/or reflection by the strata of coal and adjacentformation.

Another sensor embodiment is shown in FIG. 21. Referring to FIG. 21, thetop control shoe 142' carries a rotatable blade 400. Blade 400 is urgedupwardly by retraction of a small hydraulic cylinder assembly 402 via alinkage having two rigidly connected arms 404, 406 disposed at an angleto each other. A transducer 408 measures the movement of arm 406. Ifblade 400 is cutting only coal, it will be urged upwardly to its fullextent by assembly 402. If layer 172 is harder rock and blade 400 beginsto enter this layer, the blade will be forced downwardly and thismovement detected by transducer 408.

Any of the top and bottom sensors may be used to make the verticalsteering and sweep needs known to the machine operator, or they may bedirectly connected to the controls for the vertical steering devices andsweep control rams for automatic steering and sweep control.

Turning now to FIGS. 8-11 there is shown one of the column modules 28.The main body of the module 28 is generally comprised of the non-movingparts of the module which are rigidly connected together. The main bodyincludes a basic framework comprising longitudinal frame members 180-196extending from end to end of the module and transverse frame members198-202. The frame members are rigidly connected at their points ofintersection by welding or in any other suitable manner. Thelongitudinal and transverse frame members may be mutually notched attheir points of intersection to allow them to cross, or the transverseframe members 198-202 may each be made up of several segments, eachsegment being disposed between two adjacent longitudinal frame membersand welded to their sides. As shown in FIG. 9, one side of the moduleincludes a number of vertical truss members 204 and diagonal trussmembers 206 extending between and rigidly attached to longitudinal framemembers 192 and 194 so that the side of the module forms a truss. Theother side of the modules is identical; it includes vertical anddiagonal truss members (not shown) extending between longitudinal framemembers 180 and 196. Rigidly connected to the basic framework formed bythe longitudinal frame members 180-196, transverse frame members198-202, and truss members 204, 206 are a top cover 208, a bottom cover210, and end covers 212 and 214.

It will thus be appreciated that the main body of the column moduledefines a generally box-like structure, particularly a rectangularparallelopiped. It should be understood that the term "box-like" is notintended to imply that all faces of the structure must be covered orthat any one face must be completely covered. Rather, the term is usedbroadly to describe the general configuration of the main body of themodule. The structure of the main body of the control module 28' issubstantially the same as that of the other column modules 28, i.e. itis of similar shape and includes longitudinal and transverse framemembers, side truss members, and top, bottom, and end covers all inapproximately the same locations as those of the other column modules.The structure of the main body of the control module differs from thatof the other modules primarily in that it includes additional framemembers which define the recesses in which the steering devices andcontrol devices are located. It will be noted that the control module28' as well as the other column modules 28 are laterally elongated justas the cutting head 30 is laterally elongated. In particular, thelateral and vertical dimensions of the main bodies of the column modules28, 28' are approximately the same as those of the cutting head 30exclusive of its outboard cutting wheels 72.

Each of the column modules 28 carries a pair of parallel helicalconveyor segments 84 extending along its length. When the column modulesare joined end-to-end, the conveyor segments 84 are also joined to formtwo parallel column conveyors 38 (FIG. 1) extending along the length ofthe column. Each of the conveyor segments 84 has its shaft 84a rotatablymounted in longitudinally spaced pillow block bearings 216 and 218mounted on transverse frame members 198 and 200 respectively. Arespective pair of bolts 224 (see FIG. 20) secures the top and bottomportions of each of the bearings 218 to each other and also totransverse frame member 200. Each conveyor segment may be comprised ofthree subs having their shafts teliscopically threadedly connected atthe bearings 216, 218 to allow assembly and disassembly. Openings 226are provided in the top of transverse frame member 200 to allow accessto the bolts 224. The front bearings 216 are similarly constructed andmounted. Access to the bearings in general is provided by doors 220 and222 in the top cover 208.

The front end of the shaft 84a of each conveyor segment 84 stops at thefront end cover 212 and is provided with a hexagonal box 230. The rearend of each shaft 84a is provided with a hexagonal pin 232 which extendsbeyond rear end cover 214. When the column modules 28 are connected, thepins 232 of the conveyors 84 in one module fit into the boxes 230 of theconveyors 84 in the next module to transmit torque all along the entireconveyor 38. It should be noted, however, that the drilling thrust istransmitted primarily by the main bodies of the column modules.Preferably, the end walls 234 of the boxes 230 and the bases 236 of thepins 232 are spaced inwardly from the ends of the main body sufficientlyto prevent longitudinal abutment, and thus thrust transmission, betweenthe conveyor segments 84.

A U-shaped trough 228 (FIG. 20) rigidly secured to appropriate ones ofthe frame members extends along the sides and bottom of each of theconveyor segments 84. The trough forms a part of the main body of themodule and defines a conduit through which the conveyor segment canconvey cuttings. The conveyor segments are disposed within the box-likestructure defined by the main body of the module and are thus protectedfrom physical injury during movement of the modules and drilling. Thetop cover 208 also protects the conveyor segments 84 from becomingjammed or damaged by debris which may fall from the ceiling of the hole.

The end covers 212 and 214 are cut away at 242 and 244 respectively toallow cuttings to pass from the troughs 228 of one module to those ofthe next module. Another trough 238 is provided in the module, runningalong its length to house hoses 239 which carry hydraulic fluid to thevarious hydraulic devices on the cutting head and control module.Electrical wiring, a water hose, and other apparatus may also be housedin trough 238. Access to the trough 238 is provided by doors 240 in thetop cover 208.

The conveyor and bearing arrangement of the control module 28' issubstantially identical to that of the other column modules 28 exceptthat the front ends of its conveyor segments 84' extend beyond the frontof its main body and do not include the hexagonal pins.

Each of the column modules 28 has a pair of laterally spaced femaleconnection assemblies 242 (FIG. 12) at its front end and a pair oflaterally spaced male connection assemblies 244 at its rear end. Theconnection assemblies comprise a modified form of the type of connectionassemblies disclosed in U.S. Pat. No. 3,805,721. As best seen in FIGS.12-14 the male connection assembly 244 comprises a pin 246 which isrigidly attached to the main body of the module 28 and extends outwardlyfrom its end. Pin 246 has a head 250 at its free end, a base 252 at itsattached end, and a groove 248 along its top and sides between the head250 and base 252. The female connection assembly comprises a plate 254rigidly mounted in the end portion of the main body of the module. Plate254 has an aperture 256 for receipt of the pin 246, and the end cover214 is cut away at 262 to expose this aperture. Behind plate 254, ahairpin locking member 258 is mounted for vertical sliding movement. Thelower end of locking member 258 has a downwardly opening slot 260 sizedto fit over the groove 248 in pin 246 (see FIG. 22).

FIGS. 12 and 14 show the locking member 258 in its raised position priorto connection of the two modules 28a and 28b. Locking member 258 extendsup through an opening 264 in the top cover 208. Locking member 258 isheld in this raised position by a counterweight 266 located inboard ofthe locking member 258. A pair of outer arms 268 and 269 extend from thecounterweight 266 and are pivoted to the main body of the module 28aadjacent the locking member 258 by pins 270. A shorter arm 284 extendsfrom counterweight 266 intermediate arms 268 and 269 and in the samedirection as arms 268 and 269. Arms 268 and 284 lie immediately adjacentthe sides of the locking member 258. Locking member 258 is raised to theposition shown in FIG. 12 by reaching through the aperture 264 to engagea notch 282 in the locking member. As the locking member is pulled upthrough aperture 264, pegs 278 extending from the sides of lockingmember 258 inboard of the pivot pins 270 will engage notches 280 in thearms 268 and 284 raising the counterweight slightly. The tendency of thecounterweight 266 to swing down and toward the end cover 214 then holdsthe locking member 258 in its upper position.

To connect the two modules 28a and 28b, they are moved toward each otheruntil pin 246 has entered the aperture 256 as far as possible. The base252 is thus aligned with plate 254, and the groove 248 is aligned withthe slot 260. The top of locking member 258 is then struck with a hammerto force pegs 278 out of notches 280, and the locking member 258 fallsdown to the position shown in FIG. 13. The slot 260 fits over groove 248snugly enough to prevent the head 250 and base 252 of the pin 246 frommoving past locking member 258 if the members 28a and 28b tend to movetoward or away from each other. It will be noted that the dimension ofthe groove 248 between head 250 and base 252 is slightly greater thanthe thickness of the lower part of locking member 258 containing slot260. Furthermore, the parts of the connecting assemblies are sized sothat there is a slight clearance between the pin 246 and the lockingmember 258 in the area of groove 248 and slot 260 and between the base252 of the pin 246 and the edges of the aperture 256 in plate 254. Thisallows for a slight flexing movement between the modules 28a and 28bwhen they are not under a longitudinal compressive load. This flexinghelps to prevent the connecting assemblies from becoming jammed withdebris or frozen up by rust, corrosion or the like. The flexibility isalso useful in preventing breakage of various parts of the equipment ifthe machine should be stuck in the hole and have to be forcefullyremoved.

Each of the modules 28 has a pair of female connection assemblies on itsfront end and a pair of male connection assemblies on its rear end. Thedrive assembly 24 of the power head 18 has female connection assemblies(to be described hereinafter) located at its front end for connectingthe drive head to the rearwardmost one of the modules 28. The controlmodule 28' has male connection assemblies only, located at its rear end,for connecting the control module 28' to the next module 28.

As mentioned above, the modules 28 are connected end-to-end to form athrust-transmitting column. The term "column" is used to describe thegroup of connected modules even though it extends generally horizontallyrather than vertically as its slenderness ratio must be such that itwill provide enough strength to transmit the drilling thrust withoutsignificant bending, whipping, or the like. This allows the column notonly to transmit thrust but to guide and control the cutting head.Guiding (or gross steering) is accomplished by disposing therearwardmost module at a suitable angle. The rigid column maintains thisgeneral direction along its length. Fine steering adjustments are madeby the above mentioned steering means on the control module. The factorsand ratios involved are determinable by use of known engineeringprinciples. The column-like characteristics of the group of connectedmodules are effected by several basic considerations including: theinternal structural rigidity and compressive strength of the individualmodules; the distribution of the thrust; and the extent of the area ofabutment between adjacent modules when they are placed in compression bythe drilling thrust.

The drilling thrust is borne primarily by the longitudinal frame members180-196 of the column modules 28. These longitudinal frame members aredistributed across the entire lateral and vertical extent of the module.In particular, there is a longitudinal frame member 180, 192, 194 or 196disposed at each of the upper and lower side edges of each module. Thusthe thrust is distributed over the entire transverse cross-sectionalarea of the module. This represents an area nearly as wide laterally asthe cutting head, and thus, the hole itself. The difference between thelateral width of the modules and that of the hole (the latter beingdetermined by the width of the cutting head including the outboardcutting wheels 72) is preferably just sufficient to allow for operationof the side steering device and to prevent the machine from becomingstuck or jammed in the hole. The width of the hole would probably notexceed that of the modules by more than 20% of the former in preferredembodiments. The vertical dimension of the cross-sectional area of themodules is preferably substantially the same as that of the cutting headwhich is in turn only slightly smaller than the minimum thickness of themineable coal seam. In short, the thrust is preferably distributed overthe greatest cross-sectional area practical.

The longitudinal frame members do not, however, act as independentthrust transmitting members as in the piror art. Rather they areincorporated in an integral, rigid main body which acts as a singlethrust-transmitting column member. The main body of each module hassufficient lateral and vertical extent and sufficient internal rigidityto make it substantially inflexible under longitudinal thrust loads towhich it will be subjected. It will also be noted that, just as thethrust is distributed over the full lateral and vertical extent of eachmodule, the area of abutment between adjacent modules also covers thisfull cross-sectional area so that there is no tendency for flexingbetween adjacent modules when they are under compressive load, i.e. thedrilling thrust (see FIG. 13). All of these factors contribute to thecolumn-like characteristics of the modules.

Turning now to FIGS. 15-19 there is shown the power head 18 of themining machine. The power head comprises a base frame 22 which rests onthe ground outside the hole. The base frame can be anchored to theground by a number of picks 284 which are pivotally mounted near thebottom of the base frame 22. Each pick 284 is rigidly connected to anupstanding link 286, and the links 286 on each side of the base frame 22are all pivotally connected to a bar 288 which extends longitudinallyalong that side. A hydraulic ram assembly 290 interconnects the bar 288and the base frame 22. Thus, by extending the ram assembly 290, the bar288 is moved rearwardly. The links 284 and connected picks 286 arerotated about their pivotal connections to the base frame 22 to theposition shown in phantom at 284' so that the picks 284 dig into theground and anchor the base frame 22.

The power head 18 also comprises a track frame 20 which is mounted onthe base frame 22. The front ends of the two frames are pivotallyconnected by horizontal pins 292 so that the rear end of the track frame20 can be raised and lowered with respect to the base frame 22 by meansof a turnbuckle assembly 294 interconnecting the rear ends of the twoframes. This vertical pivotal movement enables the track frame to beused to guide the thrust-transmitting column at an angle whichcorresponds generally to the inclination of the coal seam while finersteering adjustments can be made by the control module as explainedabove.

The drive assembly 24 is mounted for longitudinal reciprocation alongthe track frame 20. The drive assembly 24 includes guide wheels 298 onboth sides which ride in respective raceways 300 at the sides of thetrack frame 20. A pair of chains 302 extend longitudinally along thesides of the track frame 20. The ends of the chains 302 are anchored tothe track frame 20 at points 304. Each of the chains 302 passes under anidler sprocket 306, over a drive sprocket 308 and under another idlersprocket 310, the respective sets of sprockets for the two chains 302being mounted on opposite sides of the drive assembly 24. The drivesprockets 308 are rotated by a reversible motor 312 also carried by thedrive assembly 24 via a chain 314 . Near the bottom of the front of thedrive assembly 24 are a pair of female connection assemlies 242' forconnecting the drive assembly 24 to the rearwardmost column module 28.The connection assemblies 242' are similar to the assemblies 242 of thecolumn modules having plates 254' containing apertures and hairpinlocking members 258'. They differ from the assemblies 242 on the columnmodules in that the locking members 258' are operated by hydrauliccylinder assemblies 352 rather than manually. The cylinder assemblies352 also eliminate the need for the counterweight arrangements forholding the locking members in their raised positions. When the rearcolumn module is connected to the drive assembly, it rests on tracks 296on the track frame 20. Thus, when motor 312 is operated, the driveassembly 24 along with the entire column of modules 28-28' and thecutting head 30 are moved forwardly or rearwardly while the tracks 296guide the column in the direction of inclination of the track frame 20.

The drive assembly also includes a pair of parallel longitudinal shafts316 whose front ends have hexagonal boxes 318 for connection to theshafts 84a of the column conveyor segments 84 of the rear column module28. The shafts 316 are driven by respective motors 321 via belts 322 andgear reducers 320 to rotate the entirety of each column conveyor, thetorque being transmitted by the hexagonal connections between conveyorsegments. The rear or outlet ends of the column conveyors are disposedadjacent the inlets of three screw type drive assembly conveyors 40.Each conveyor 40 includes a helical conveyor segment 324 having a shaft324a and encased in a tube 326. The conveyors slant upwardly andrearwardly from the column conveyors. The shafts 324a are driven by amotor 328 via belts 330. The outlets of conveyors 40 communicate withchutes 333 which deposit the cuttings on the transverse belt conveyor 42mounted on the drive assembly. Conveyor 42 is driven by motor 332 viabelt 336. The cuttings are carried to one side of the power head byconveyor 42. A longitudinal belt conveyor 44 (see FIG. 1) runs along theside of the drive head 18 to catch the cuttings from transverse conveyor42 regardless of the position of the drive assembly on the track frame.Conveyor 44 in turn carries the fragments or cuttings to the rear of thepower head to conveyor 46 for loading.

In addition to the primary drive means comprising chains 302, sprockets306-310, motor 312, and belt 314, the power head 18 includes auxiliarydrive means which provide additional force to move the drive assembly 24relative to the track frame 20 if the cutting head 30 or column ofmodules 28-28' should become jammed in the hole. The auxiliary drivemeans comprise a pair of hydraulic ram assemblies 344, preferablyreversible, disposed on opposite sides of the drive head. Each of theassemblies 344 has its cylinder 348 connected to the drive assembly. Thepiston rods 346 of the assemblies 344 are connected to each other by atransverse tube 340 which lies between and free of the sides of thetrack frame 20. A second tube 342 is slidably mounted in each end oftube 340. The track frame has along each side a number of vertical bars338. When the auxiliary drive means is not in use, the tubes 342 aredisposed wholly within the tube 340 free of the sides of the track frame20 as shown in the lower half of FIG. 19. When it is desired to use theauxiliary drive means, the tubes 342 are gripped with a suitable tooland pulled laterally outwardly between respective pairs of the bars 338as shown in the upper half of FIG. 19. The tube 342 will abut one of thebars 338 between which it lies (the rearwardmost one of the cutting headis to be pulled back; the forwardmost one if the cutting head is to bepushed forward) to fix the piston rods 346 with respect to the trackframe 20 against motion toward the abutting bar 338. The ram assemblies348 are then operated, either alone or with the primary drive means, toforceably move the cutting head.

All of the rotary motors and ram assemblies on the drive head, cuttinghead, and control module are preferably hydraulic and are operated bycontrols in a single control station outside the hole. This controlstation may be in the cab of the crane 34 and the controls are connectedto the various hydraulic devices by any suitable means, many of whichare known in the art. Hoses for the hydraulic fluid for these variousassemblies are carried by two of four spools 350 (only one of which isshown) mounted on the rear of the track frame 20 and pass through thetroughs 238 in the column modules 28. The other two spools 350respectively carry a water hose, for a cooling spray for the cuttingpicks, and an electric cable; these also pass through troughs 238.Readings from the sensing means are also conveyed to the control stationby electronic or other suitable means. It will be appreciated that powermeans other than hydraulic motors and ram assemblies could be used forthe various operations of the parts of the mining machine. However it ispreferably to have the controls for all the power means and the readoutsfrom the sensors all located in a single station outside the hole.

It will be appreciated that many modifications of the above embodimentscan be made without departing from the spirit of the invention. It isthus intended that the scope of the invention be limited only by theclaims which follow.

I claim: .[.1. A mining machine comprising: carried by a respective oneof said column modules..].
 3. A mining machine as recited in claim.[.2.]. .Iadd.43 .Iaddend.wherein each of said column modules has a mainbody which generally defines a rectangular parallelopiped.
 4. A miningmachine as recited in claim .[.2.]. .Iadd.43 .Iaddend.wherein the mainbody of each of said column modules comprises a top cover, and whereineach of said conveyor segments is disposed beneath the top cover of itsrespective column module.
 5. A mining machine as recited in claim 4wherein the main body of each of said column modules defines a box-likestructure and wherein each of said conveyor segments is disposed withinthe box-like structure of its respective column module. A mining machineas recited in claim 5 wherein the main body of each of said columnmodules further comprises a bottom cover, two end covers, and aplurality of bracing members at each of its sides.
 7. A mining machineaccording to claim 5 wherein said column conveyor is a screw typeconveyor.
 8. A mining machine as recited in claim 7 comprising two suchcolumn conveyors carried by said column extending along substantiallythe entire length of said column and disposed parallel to each other. 9.A mining machine as recited in claim 7 wherein each of said columnmodules further includes a trough extending along the sides and bottomof the respective one of said conveyor segments.
 10. A mining machine asrecited in claim .[.2.]. .Iadd.43 .Iaddend.wherein the forwardmost oneof said column modules is a control module and includes means forsteering said cutting head.
 11. A mining machine as recited in claim 10wherein said steering means includes a side steering shoe selectivelylaterally extensible and retractable from one side of said controlmodule and wherein said cutting head includes means operative to causesaid cutting head to bear laterally toward said one side.
 12. A miningmachine as recited in claim 11 wherein said cutting head comprises alateral shaft, means for rotating said shaft and a helical center cutterwound to cause said cutting head to bear toward said one side whencutting.
 13. A mining machine as recited in claim 11 wherein saidcontrol module includes means operative to detect the presence of apillar of formation at the side of said control module opposite said oneside.
 14. A mining machine as recited in claim 13 wherein said means fordetecting the presence of said pillar is also operative to detect afactor indicative of the strength of said pillar.
 15. A mining machineas recited in claim 12 wherein said cutting head further comprises apair of side cutters disposed at opposite sides of said center cutterlaterally outwardly of said column modules, cutting head conveyor meansfor conveying formation fragments cut by said cutting means to saidcolumn conveyor, and scoop means for directing said formation fragmentsinto said cutting head conveyor means.
 16. A mining machine as recitedin claim 10 wherein said steering means includes a bottom steering shoeselectively vertically extensible and retractable from the bottom ofsaid control module.
 17. A mining machine as recited in claim 16 furthercomprising means for pivoting said cutting head vertically with respectto said control module.
 18. A mining machine as recited in claim 17wherein said control module includes means operative to detect a factorindicative of the thickness of a stratum of formation above said controlmodule.
 19. A mining machine as recited in claim 16 wherein saidsteering means includes two such bottom steering shoes disposed adjacentopposite sides of said control module and independently verticallyextensible and retractable from the bottom of said control module.
 20. Amining machine as recited in claim 10 wherein said control moduleincludes a top control shoe selectively vertically extensible andretractable from the top of said control module to bear against theformation above said control module for reaction to forces generated bysaid cutting head.
 21. A mining machine as recited in claim 20 whereinsaid control module includes two such top control shoes independentlyselectively extensible and retractable from the top of said controlmodule.
 22. A mining machine as recited in claim .[.2.]. .Iadd.43.Iaddend.wherein said power head comprises a track frame, a driveassembly mounted on said track frame and removably connected to therearwardmost one of said column modules, and primary reversible drivemeans for moving said drive assembly longitudinally along said trackframe.
 23. A mining machine as recited in claim 22 wherein said trackframe includes a chain extending lengthwise of said track frame andhaving its ends anchored to said track frame, and wherein said driveassembly includes a sprocket wheel engaging said chain and a reversiblemotor operatively connected to said sprocket wheel to rotate saidsprocket wheel and thereby move said drive assembly along said chain.24. A mining machine as recited in claim 22 wherein said power headfurther comprises auxiliary drive means for moving said drive assemblylongitudinally along said track frame.
 25. A mining machine as recitedin claim 24 wherein said auxiliary drive means includes a hydraulic ramassembly including a pair of telescoping members, one of said membersbeing connected to said drive assembly, and means for selectively fixingthe other of said telescoping members against motion in one directionwith respect to said track frame.
 26. A mining machine as recited inclaim 22 wherein said power head further comprises power head conveyormeans for conveying formation fragments from said column conveyor to therear end of said power head.
 27. A mining machine as recited in claim 22wherein said track frame comprises guide means for guiding said columnis the general longitudinal direction of said track frame.
 28. A miningmachine as recited in claim 27 wherein said power head further comprisesa base frame, said track frame being pivotally mounted on said baseframe, and means for selectively vertically pivoting the rear end ofsaid track frame with respect to said base frame.
 29. A mining machineas recited in claim 28 wherein said power head further comprises meansfor anchoring said base frame to the ground. .Iadd.
 30. A mining machinefor mining mineral formations comprising:a cutting head including meansfor cutting a mineral formation, the dimensions of said cutting headfrom side-to-side being substantially greater than its verticaldimension, a power head disposed remote from said cutting head, a thrusttransmitting column disposed intermediate said cutting head and saidpower head, said thrust transmitting column being nonrotatable about itslongitudinal axis and comprising a plurality of reusable column modulesremovably connected in end-to-end engagement, a forwardmost one of saidcolumn modules being removably connected to said cutting head and arearwardmost one of said column modules being removably connected tosaid power head, each of said column modules comprising a box-likestructure having a substantially greater dimension from side-to-sidethan vertically and being effective to transmit thrust as a unitarymember, said plurality of column modules collectively functioning as asingle thrust transmitting column member, a column conveyor sectiondisposed within the box-like section of, and carried by, each saidcolumn modules, first means releasably securing adjacent column modulesin thrust transmitting engagement, said column conveyor sections beingnon-thrust transmitting, said power head being effective to selectivelyapply forward or rearward force to the rearwardmost column module ofsaid thrust transmitting column to selectively urge said cutting headforwardly into said mineral seam to facilitate cutting said mineralseam, or rearwardly thereof to facilitate removal of said cutting headand column from said mineral formation. .Iaddend. .Iadd.
 31. The miningmachine of claim 30 in which said column modules are in abutment over asubstantial portion of the cross-sectional area thereof. .Iaddend..Iadd.32. The mining machine of claim 30 in which each said column modulecomprises a top cover and each of said conveyor segments is disposedbeneath the top cover of its respective module. .Iaddend..Iadd.
 33. Themining machine of claim 30 in which each said column module issubstantially as wide as said cutting head. .Iaddend..Iadd.
 34. Themining machine of claim 30 in which each said column module issubstantially as high as said cutting head. .Iaddend..Iadd.
 35. Themining machine of claim 30 in which each said column module issubstantially as wide and as high as said cutting head. .Iaddend..Iadd.36. The mining machine of claim 30 in which said cutting head means forcutting a mineral formation is carried by a control module and includesmotor means carried by said control module. .Iaddend. .Iadd.
 37. Themining machine of claim 30 further including means for pivoting saidcutting head vertically. .Iaddend..Iadd.
 38. The mining machine of claim30 in which said conveyor sections are screw conveyor sections..Iaddend..Iadd.
 39. The mining machine of claim 30 further comprisingsecond means releasably interconnecting conveyors of adjacent columnmodules, said second means being effective to transmit a drive force forsaid conveyors, but not being effective to transmit thrust..Iaddend..Iadd.
 40. The mining machine of claim 39 wherein said powerhead comprises a track frame, a drive assembly mounted on said trackframe and removably connected to the rearwardmost one of said columnmodules, and reversible drive means for moving said drive assemblylongitudinally along said track frame, said drive assembly includingmeans for driving said conveyor to the adjacent column module withoutapplying substantial thrust thereto. .Iaddend..Iadd.
 41. The miningmachine of claim 30 wherein said power head includes means toselectively vertically tilt said column module. .Iaddend. .Iadd.
 42. Amining machine comprising: a cutting head including means for cutting anearth formation, the dimension of said cutting head from side to sidebeing substantially greater than its vertical dimension; a nonrotatablethrust-transmitting column connected to said cutting head and extendingrearwardly therefrom, the dimension of said column from side to sidebeing substantially greater than its vertical dimension, and said columnhaving a non-thrust-transmitting column conveyor carried thereby andmovable relative thereto and extending along substantially the entirelength of said column; and a power head connected to said columnrearwardly of said cutting head and operative to thrust said cuttinghead forward into an earth formation by means of said column, and towithdraw said cutting head and column from said earth formation..Iaddend. .Iadd.
 43. A mining machine comprising: a cutting headincluding means for cutting an earth formation, the dimension of saidcutting head from side to side being substantially greater than itsvertical dimension; a thrust-transmitting column connected to saidcutting head and extending rearwardly therefrom, the dimension of saidcolumn from side to side being substantially greater than its verticaldimension, and said column having a non-thrust-transmitting columnconveyor carried thereby and extending along substantially the entirelength of said column; said column comprising a plurality of columnmodules removably connected in end-to-end relation, a forwardmost one ofsaid column modules being removably connected to said cutting head and arearwardmost one of said column modules being removably connected tosaid power head, said column conveyor comprising a plurality of conveyorsegments disposed in end-to-end relation, each of said conveyor segmentsbeing carried by a respective one of said column modules, and a powerhead connected to said column rearwardly of said cutting head andoperative to thrust said cutting head forward into an earth formation bymeans of said column. .Iaddend.